Electronic structure of nitric oxide adducts of bis(diaryl-1,2-dithiolene)iron compounds: four-membered electron-transfer series [Fe(NO)(L)2]z (z = 1+, 0, 1-, 2-).

Four members of the electron-transfer series [Fe(NO)(S(2)C(2)R(2))2]z (z = 1+, 0, 1-, 2-) have been isolated as solid materials (R = p-tolyl): [1a](BF4), [1a]0, [Co(Cp)2][1a], and [Co(Cp)2]2[1a]. In addition, complexes [2a]0 (R = 4,4-diphenyl), [3a]0 (R = p-methoxyphenyl), [Et(4)N][4a] (R = phenyl), and [PPh(4)][5a] (R = -CN) have been synthesized and the members of each of their electron-transfer series electrochemically generated in CH(2)Cl(2) solution. All species have been characterized electro- and magnetochemically. Their electronic, Mössbauer, and electron paramagnetic resonance spectra as well as their infrared spectra have been recorded in order to elucidate the electronic structure of each member of the electron-transfer series. It is shown that the monocationic, neutral, and monoanionic species possess an {FeNO}6 (S = 0) moiety where the redox chemistry is sulfur ligand-based, (L)2-(L*)1-: [Fe(NO)(L*)2]+ (S = 0), [Fe(NO)(L*)(L)]0 <--> [Fe(NO)(L)(L*)]0 (S = 1/2), [Fe(NO)(L)2]- (S = 0). Further one-electron reduction generates a dianion with an {FeNO}7 (S = 1/2) unit and two fully reduced, diamagnetic dianions L2-: [Fe(NO)(L)2]2- (S = 1/2).

Electronic structure of mononuclear bis(1,2-diaryl-1,2-ethylenedithiolato)iron complexes containing a fifth cyanide or phosphite ligand: a combined experimental and computational study.

A series of mononuclear square-based pyramidal complexes of iron containing two 1,2-diaryl-ethylene-1,2-dithiolate ligands in various oxidation levels has been synthesized. The reaction of the dinuclear species [Fe(III)2(1L*)2(1L)2]0, where (1L)2- is the closed shell di-(4-tert-butylphenyl)-1,2-ethylenedithiolate dianion and (1L*)1- is its one-electron-oxidized pi-radical monoanion, with [N(n-Bu)4]CN in toluene yields dark green crystals of mononuclear [N(n-Bu)4][Fe(II)(1L*)2(CN)] (1). The oxidation of 1 with ferrocenium hexafluorophosphate yields blue [Fe(III)(1L*)2(CN)] (1ox), and analogously, a reduction with [Cp2Co] yields [Cp2Co][N(n-Bu)4][Fe(II)(1L*)(1L)(CN)] (1red); oxidation of the neutral dimer with iodine gives [Fe(III)(1L*)2I] (2). The dimer reacts with the phosphite P(OCH3)3 to yield [Fe(II)(1L*)2{P(OCH3)3}] (3), and [Fe(III)2(3L*)2(3L)2] reacts with P(OC6H5)3 to give [Fe(II)(3L*)2{P(OC6H5)3}] (4), where (3L)2- represents 1,2-diphenyl-1,2-ethylenedithiolate(2-). Both 3 and 4 were electrochemically one-electron oxidized to the monocations 3ox and 4ox and reduced to the monoanions 3red and 4red. The structures of 1 and 4 have been determined by X-ray crystallography. All compounds have been studied by magnetic susceptibility measurements, X-band EPR, UV-vis, IR, and Mössbauer spectroscopies. The following five-coordinate chromophores have been identified: (a) [Fe(III)(L*)2X]n, X = CN-, I- (n = 0) (1ox, 2); X = P(OR)3 (n = 1+) )3ox, 4ox) with St = 1/2, SFe = 3/2; (b) [Fe(II)(L*)2X]n, X = CN-, (n = 1-) (1); X = P(OR)3 (n = 0) (3, 4) with St = SFe = 0; (c) [Fe(II)(L*)(L)X]n <--> [Fe(II)(L)(L*)X]n, X = CN- (n = 2-) (1red); X = P(OR)3 (n = 1-) (3red, 4red) with St = 1/2, SFe = 0 (or 1). Complex 1ox displays spin crossover behavior: St = 1/2 <--> St = 3/2 with intrinsic spin-state change SFe = 3/2 <--> SFe = 5/2. The electronic structures of 1 and 1(ox) have been established by density functional theoretical calculations: [Fe(II)(1L*)2(CN)]1- (SFe = 0, St = 0) and [Fe(III)(1L*)2(CN)]0 (SFe = 3/2, St = 1/2).

Dinuclear Bis(1,2-diaryl-1,2-ethylenedithiolato)iron complexes: [FeIII2(L)4]n (n = 2-, 1-, 0, 1+).

The electronic structures of four members of the electron-transfer series [Fe2(1L)4]n (n = 2-, 1-, 0, 1+) have been elucidated in some detail by electronic absorption, IR, X-band electron paramagnetic resonance (EPR), and Mössbauer spectroscopies where (1L)(2-) represents the ligand 1,2-bis(4-tert-butylphenyl)-1,2-ethylenedithiolate(2-) and (1L*)- is its pi-radical monoanion. It is conclusively shown that all redox processes are ligand-centered and that high-valent iron(IV) is not accessible. The following complexes have been synthesized: [FeIII2(1L*)2(1L)2]0 (1), [FeIII2(2L*)2(2L)2].2CH2Cl2 (1') where (2L)(2-) is 1,2-bis(p-tolyl)-1,2-ethylenedithiolate(2-) and (2L*)- represents its pi-radical monoanion, [Cp2Co][FeIII2(1L*))(1L)3].4(toluene).0.5Et2O (2), and [Cp2Co]2[FeIII2(1L)4].2(toluene) (3). The crystal structures of 1' and 2 have been determined by single-crystal X-ray crystallography at 100 K. The ground states of complexes have been determined by temperature-dependent magnetic susceptibility measurements and EPR spectroscopy: 1' and 1 are diamagnetic (S(t) = 0); 2 (S(t) = 1/2); 3 (S(t) = 0); the monocation [Fe(III)2(1L*)3(1L)]+ possesses an S(t) = 1/2 ground state (S(t) = total spin ground state of dinuclear species). All species contain pairs of intermediate-spin ferric ions (S(Fe) = 3/2), which are strongly antiferromagnetically coupled (H = -2JS(1).S(2), where S1 = S2 = 3/2 and J = approximately -250 cm(-1)).